Picometre-scale real-time drift correction in TEM and STEM by dynamic control of the specimen stage for atomic-resolution imaging
In this work, we show how the specimen drift can be actively compensated by controlling the stage with precision down to the picometre scale. We do this by dynamic control, a generic real-time feedback framework designed to actively stabilize electron microscopy experiments by continuously monitoring an experimental variable from the detector data stream and compensating its evolution during acquisition. The framework, applicable to a broad range of controllable experimental instabilities, includes automated calibration procedures, operates in parallel with image acquisition and is implemented as a software plugin without requiring any hardware modification of the microscope. Results for live drift correction are shown for a selection of TEM and STEM instruments using conventional mechanical stages as well as piezoelectric stages. Experimental results are presented for medium resolution TEM, high-resolution TEM, HR-STEM and in situ observations. With piezoelectric stages, specimen stabilization down to the picometre scale was achieved allowing drift-corrected atomic-resolution imaging. Specimen stage-based stabilization significantly improves long-exposure imaging and in situ experiments by increasing the effective exposure time, preserving the field of view, maintaining identical optical conditions and eliminating the need for numerical alignment of large datasets. Beyond the specific application presented here, dynamic control provides a versatile framework for real-time regulation of electron microscopy experiments and opens new perspectives for quantitative imaging, automated in situ studies and multimodal acquisitions.